Save draft in localstorage if runbox7 is offline

[tadzik]

Is your feature request related to a problem? Please describe.
When the internet connection (or Runbox API) goes down intermittently, a drafted message is not saved anywhere. With as little as clicking away to another folder and back to drafts, the typed in content is lost.

Describe the solution you'd like
When Runbox7 is offline, a draft should be saved locally (in browser's localStorage or similar), so that the typed in message is not completely lost.

Describe alternatives you've considered
Perhaps it's a sensible failsafe to save drafts in both places at the same time. This could lead to conflicts if the versions diverge, so they'd either need a timestamp (timezone-agnostic, just in case :)), a heuristic like "longer draft wins" (could backfire) or a "which draft do you want to use" screen (lots of work for an edgecase).

Additional context
Happy holidays!

[tadzik]

Just as I finished typing this, my connection to Runbox7 API came back up, and now I have two drafts that I didn't have a moment ago – so not only there was no actual data loss (presumably because the underlying API requests were still being retried under the hood, and I didn't refresh the page or anything like that), I now have a version history. Cool :D But the feature request still stands :)

[gtandersen]

Thanks for the suggestion @tadzik -- and Happy Holidays from us! :)